Wall Turbulence Control and Skin-Friction Drag Reduction with Novel Surface Microstructures

Skin-friction drag is responsible for energy loss for ships, aircraft, and the trucking industry. This project explores innovative methods of reducing skin-friction drag using computations and experiments. One of the promising methods for reducing skin-friction drag is to dampen wall turbulence passively using surface microstructures.

While a substantial amount of effort has been made to advance wall techniques, the process is not yet completely understood. The primary aim of this project is to provide a fundamental understanding of the underlying physics of these novel surface microstructures and show that they can provide systematic control of wall turbulence to minimize skin-friction drag.

The project outcomes will be disseminated to broader communities through many educational and outreach activities, such as undergraduate research programs, scientific publications, conference presentations, and summer science camps to K-12 students and teachers.

A micro airfoil structure, which is a newly proposed surface microstructure, is expected to achieve unique turbulence control capabilities due to its well-defined 3D geometry. The main objectives of the project are: (i) to demonstrate the turbulence control capability using the micro airfoil structure, (ii) to identify the connections between the control inputs created by the micro airfoil structure and the responses of skin-friction drag, (iii) to understand the fundamental mechanisms of the turbulence control and skin-friction drag reduction by the micro airfoil structure, and (iv) to recommend the optimum configurations of the single and arrays of micro airfoil structure for the maximum reduction of skin-friction drag.

Direct numerical simulation and large eddy simulation will be used to compute fundamental flows, and particle image velocimetry will be used to measure velocities in the turbulent boundary layer. The fundamental knowledge obtained through this project will provide insight to answer the long-lasting questions about the dynamics of wall-bounded turbulent flows.

The unique turbulence control techniques achieved by the micro airfoil structure will provide guidance to other research areas in aerospace, mechanical, chemical, and ocean engineering where turbulence control may lead to drag reduction. This project is jointly funded by Fluid Dynamics and the Established Program to Stimulate Competitive Research (EPSCoR) programs.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.